Variable volume internal chamber type hydraulic pump



Aug. 11, 1959 R. w. BRUNDAGE 2,393,862

. VARIABLE VOLUME INTERNAL CHAMBER TYPE HYDRAULIC PUMP Filed March 29, 1955 j FIG. I" FIG. 2

IN V EN TOR.

FIG.3 .1 FIG-4 ROBERT W. B RUNDADGE BY ATTORNEY increase or decrease in volume.

United States Patent VARIABLE VOLUME INTERNAL CHAMBER TYPE HYDRAULIC PUMP This invention pertains to the art of hydraulic. pumps and more particularly to a hydraulicpump of the internal chamber type having a variable volume output at constant-rotational speed.

The invention is particularly adapted to internal gear type pumps and will be described with particular.reference thereto, although it willbe appreciated that the invention is equally applicable to other typesv of pumps such as, but not limited to, vane type pumps- Pumps of the type to which this invention generally pertain include inner and outer members relatively rotatable on spaced axes whereby to provide an eccentric space between the two members. Means are provided for dividing this eccentric space into a plurality of smaller chambers. Such means, as are known, may comprise gear teeth on both members or vanes on the rotatable member which reciprocates in and out as the rotatable member rotates. With gear teeth, the outer member has one or more teeth than the inner member and the teeth are so formed that they may advance relative to each other while being in sealing engagement at all times.

As the members rotate, the small chambers constantly increase in volume from a point of zero volume to a point spaced 180 therefrom where the gear teeth are out of mesh entirely or the vanes are fully extended. From this latter point to the first mentioned point, i.e. through bers to divide the eccentric space thus provided into a plurality of chambers which constantly increase and decrease in volume as the members are rotated, a housing surrounding the members, inlet and outlet passages comnunicating with the chambers, and lands between the mlet and outlet passages, which apparatus overcomes all of the above referred to difiiculties and permits the volume output of the pump to be varied at will without loss of efliciency, and which is simple in construction and easily operated.

In accordance with the invention, the land dividing the inlet passage from the outlet passage in the direction of rotation is permanently fixed opposite the point of maximum volume of the chambers while the land between the outlet and inlet passages inthe direction of rotation is made, relatively adjustable. This last mentioned land may be adjustable either in the direction of rotation or contra to the direction of rotation. Preferably, however, and for maximum efficiency it is adjustable in the direction of rotation from a point opposite the point of volume of the chambers around to, but not beyond, the point of maximum volume. As the land adjacent to the point of maximum volume always has some dimensions it will be appreciated that the rotation of the movable land will have a limit somewhat less than 180".

With this arrangement it will be appreciated that if the 1 movable land is located opposite the point of minimum a second arc 015180, the volume of the small chambers decreases as the members rotate.

.lationship therewith. This housing has an internal passage communicating both with all the chambers as they the passage to provide an inlet passage and an outlet or discharge passage.

For each revolution of the inner and outer members there is a constant change in the volume of the chambers A pair of lands separate so that with a hydraulic pump, that is one pumping a non-compressible fluid, the volume of the fluid pumped will be constant for any constant speed of the pump. As these pumps are best driven from constant speed electric motors or the like, the problems of varying the vol- ;ume output with such constant driving speed has always been a problem.

The problem primarily manifests itself where a constant speed hydraulic pump must supply fluid under pressure to intermittently operating or varied speed loads, such ashydraulic presses or the like. Heretofore such constant pressure was obtained by pressure regulating by-pass valves or accumulator tanks or by turning the pump on and off, i.e. variable speed.

So far as I am aware no one has heretofore proposed an eflicient variable volume, constant speed hydraulic pump of the type referred to or one having a constant pressure for a variable volume load.

The present invention contemplates apparatus of the type described including the inner and outer members relatively rotatable on spaced axes, means on said memvolume of the chambers, the pump will function as any other pump of the type to which this invention pertains. However, if the land is moved in the direction of rotation to a point, say for example, midway between the point of minimum volume and the point of maximum volume ofthe chambers, fluid will and can flow through the now extended discharge passage to the chambers as they increase in volume. This fluid is under pressure and acts on the now enlarging chambers like a motor and its energy is regained. I

The principal object of the invention is the provision of a new and improved constant velocity, variable volume, hydraulic pump which is simple in construction, eflicient in operation, and which gives substantially full variation of the volume output of the pump with a high etiiciency.

Another object is a constant speed hydraulic pump which may be so controlled as to have a constant pressure output with a variable volume load.

Another object of the invention is the provision of a new and improved internal gear or vane type hydraulic pump having a variable volume output at high efiiciency at all volumes.

Still another object of the invention is the provision of a new and improved hydraulic pump including in combination a pair of members mounted one inside the other for relative rotation on spaced axes with means dividing the eccentric space thus formed into a plurality of small chambers which expand and contract from minimum to maximum volume as the members rotate, inlet and outlet passages separated by lands communicating with the chambers, one of which lands is located adjacent the point of maximum volume of the chambers and is fixed and the other of which is adjustable preferably from the point of minimum volume to a point towards the point of maximum volume in the direction of rotation. V

The invention may be comprised in certain parts and combination of parts a preferred embodiment of which will be described in detail in this specification and illustrated in the accompanying drawing which in a part hereof and wherein:

Figure 1 is a side cross-sectional view of a hydraplic pump oi the internal gear type embodying the present invention.

hers respectively, as shown.

Figure 2 is a cross-sectional view of Figure 1 taken appreximately on the line 2'2thereof.'

Figure 3 is a cross-sectiohal view of Figure 1 taken approximately. on the line 3-3 thereof,;and,- p Figure 4 is ac'ross-sectio ial'view of Fig'u'reYhtakeri approximately on the liiie 4 -4 thereof shdwihg'ifi greater detail the adjustable stop by' which 'the'voliitiie output of the pump may bev'aried. E

Referririg to the drawings wherein the showings here: the purposes of illustrating the inventienoaly anan'ot for the purposes of same, the figures show a by draulic pump comprised of a housing arid a cover plate 11 defining an interior closed chamber; A gear 12 having inwardly facing teeth 13'is ,rotatalbly supported-in this chamber on an axis14l. Positioned on the inside of this gear" 12 is an externally toothed gear 15 having outwardly facing teeth 16 of a lesser number than the iiiwardly facing teeth 1'3'of'the'ririg gear The externally toothed gear'1'5 is keyed to a shaft 18' which extends through an opening in the cover'plate 1'1 and is adapted to be mechanically connected to a motor, not shown.- This shaft 18 and the gear 15 rotate on an axis 19. 7

It will be noted that the' axes 14 and 19'are spaced one from the other so that the surfaces of the'ge'arblS and of the gear 12 are eccentric to each other and in effect provide an eccentric space between the two mem hers. The teeth 13 and 16 alternately mesh and slide over each other While all'the time remaininglin' contact to'divide this eccentric space into a plurality'of' chambers 20 which chambers alternately expand and contract'as the two members rotate in housing 10'. As shown'inFigure 2} the members rotate in a clockwise direction'but obvio'usly they may rotate in" a counter-clockwise direction; In the embodiment shown, at theupperm'ost point i'ndi=- cated at A in the rotation of the two members, the teeth 13 and 16 are fully meshed and'the'volumeof the chain'- ber' 20 is zero or substantially so. As the chambers approach this point they are contracting. As the chambers leave this point they expand, that is to say, just prior to reaching the point A the chambers discharge fluid under pressure and immediately after they pass this point'they suck in fluid.

Beyond the point A thechamber 20 expands through 180" of its rotation until it reaches a point B at the lowerniost point in the arc of rotation where the chamber 20 ceases to further expand and commences to contract; At this point the chamber 20 changes from an intake chamber to a discharge chamber. a I

The particular shape and formation of the teeth 13 and v16 are conventional in theart and form no partof the present invention; In eficct, they are means co-acting between the two membersto divide the eccentric. space into a plurality of chambers which can expand and contract in volume as one or both of the membersr otate's'.

Obviously in the-case of a gear typepump as described both members must rotate while in the case of a vane type pump either one or both of the members may rotate.

communication with an opening from chambers 20 as they expand and contract.

A fixed land 31 at the point B and a movable land 35 at the point A separate the manifolds 28, 29 into inlet and outlet manifolds respectively. The land 31 is integral with the housing 10. This land has an axial thickness equal to the depth of the manifolds 28, 29 and has sealing engagement with the outer periphery 32 on a control member 33 having at one. point on" its periphery 31 a radially outwardly extending land 35 which extends into sealing but-sliding engagement with the radially inwardly facing surface 36 forming the manifolds 28 and 29. Both" lands have a circumferential width equal to approximately one tooth pitch, as is conventional, that is, the lands have a" path of movement width slightly greater than the path of movement width of the openings from the chambers facing the manifolds.

In accordance with the invention, the land 31 isfixed,

' this being-the landpositio'ned opposite the point of maxi- In the embodiment of the invention shown; both'gears 12 and 15 have the same axial thickness. The right-hand side of these gears bears against the inner surface of the cover plate 11 and is in sealing engagement therewith.

The side of the housing remote from the cover plate 11 is provided with an inlet port 25 and a diametrically opposite outlet port 26 through which the fluid bcih'g pumped can enter and leave the pump respectively. These are located at points close to but spaced from the points of maximum volume and minimum volume of ',the ohamear 15 so as to be continuously incommunicationwith "W gfrom the chambers. 20. A:similar'm 'f 1d 29 communicates with the outlet port 26 andis-alsoin enlarging, chambers;

mum volume of the chambers 20. The land 35 is, in accordance with the invention, movable or. adjustable from the point A which as previously pointed out is the point of'mininiurn volume of the chambers 20in either direction but preferably in the direction of rotation so that the volumeoutput of the pump may be varied at will. It will'be'noted that the periphery 32 of the control member. 33' is co-a'xial with the axis of rotation 19. The control member 33' includes an axially extending hub 39 intowhich the left-hand end of the shaft 18' extends and is' rotatab'ly supported. The outer surface of the hub 39 is journaled for selective rotation in a suitable recess in the housing 10.

Means are provided for the'purpose of rotating the control member 33' to adjustably position its land 35. Inthe'enibodiment' shown, the outer surface of the hub 39' is' provided w'ithg'ea'r teeth 41 which mesh with the teeth oh aworrh'4'3; This worm 43'is rotatably supported on a shaft spaced from and perpendicular to the axis of rb'tation of the shaft 19: and extends-outwardly of the housingwhere' a handle 45 is provided for rotating the worm 43. Obviously, asth'e worm wheel 43 is rotated,

the control member 33' will likewise be rotated through a eontrolledand desiredamount of arc. The position of this land ma be automatically controlled if desired, as will appear, to vary the volume output in relation to the output pressure and thus obtain constant pressure output.

Iii operation, the shaft 18 is rotated in a clock-wise direction; The chambers 20' constantly increase in volume frointhe' point A to the point B and then constantly .decreasein volume from the point Bto the pointA always speaking in the" direction of rotation. With the land-35 positioned as isshown in Figure 4 and in dotted lineas lto'. contract the'fiuid will be squeezed'out into the manifold 29 and then outwardly throughthe outlet port26;

he assumed, however, that theland'35- is rotated in' the direction of rotation to the position showri-in'thc dotted lines of Figure 4, then an entirely difierent' action takes' place. As the chambers'20 enlarge from thepoint A goingtowarfd the land, fluid will flow'thr'oug'h the outlet manifold 29', now enlarged or lengthened, to fill these This fluid is under pressure and from the point-A to the point where the land is shown in Figute 4 the pump actually acts'like a motor sothat the energy of the fluid is regained. After the chambers 20 pass the land 35. as shown in dotted lines in Figure 4,

fluid can flow into the chambers through the inlet passage ZSinthe-usual manner;

In effect, some of the dischargefluid of thepuinp is being by-passed intemally of the pump to some of the increasing volumechambers, but without lossof pressure .of the lay-passed fluid. Thus, this.fiuid, as above pointe'd out, is impressed on chambers which are expanding in volume and a motor action results. There is no loss of energy such as would be the case if the output pressure of the pump were passed through the actual inlet port of the pump.

It would appear that a similar variation in the volume output of the pump could be obtained by rotating the land 35 counter to the direction of rotation. While this is so, another detrimental efiect not immediately apparent comes into play. The chambers, as they approach the point A in the direction of rotation, are decreasing in volume. The land 35 has a circumferential width equal to approximately one tooth pitch. Thus, for a short portion of the rotation, fluid can not escape from this contracting chamber. A trapping action results where no fluid can get out and extremely high pressures can result, which pressures might exceed the design pressure of the pump.

On the other hand, with the land 35 rotated in accordance with the invention, the chambers are enlarging. Instead of a trapping action, a vacuum will be created in the chambers as they pass the land 35 in whatever position it may be in. Such vacuum can never exceed 14.7 pounds per square inch in relation to the outside atmosphere, or can never exceed the actual operating pressure of the pump plus 14.7 pounds per square inch. Such pressure variations are a very small percentage in relation to the maximum pressures usually employed with hydraulic pumps.

This vacuum has a further desirable effect, that is, it tends to suck or draw the parts together, creating an improved sealing action between the surfaces.

It will also appear that if the land 31 were rotated in the direction of rotation, this same trapping action would immediately result, with its undesirable effect.

If the land 31 were rotated in a direction counter to the rotation, then the fluid, in order to flow into the expanding chambers thus opened to the discharge pressure, would have to reverse direction of flow in order to reach these chambers. This results in a loss of efficiency.

The location of the inlet and the outlet port in the housing of the pump is only schematic and may be otherwise if desired. For example, the inlet and outlet port could extend radially outwardly through the sides of the housing 10.

Using the present invention, it is possible to have a pump rotating at a constant speed deliver fluid to a load at a constant pressure, that is to say, the volume output of the pump may be varied from zero to maximum in proportion to the variation in the output pressure on the pump from a maximum, pre-set value to a value below said pro-set value. Thus, a hydraulic motor could be employed to position the land 35, said hydraulic motor being operated through a pressure sensitive valve or the like. Such hydraulic motor could rotate the shaft 44 directly in place of the handle 45, or could be connected directly to the disk 33. In fact, a vane type motor, direct-com nected to the disk 33 could be incorporated in the housing 10, adjacent to, but spaced from, the disk 33 with its movable land 35, such vane motor being operated through a pressure sensitive valve by the output pressure of the pump, or alternatively, the vane motor could operate against a calibrated spring which in conjunction with the vane motor would control the position of the land 35 in relation to the output pressure of the pump.

It will be appreciated that the invention is equally applicable to a vane type pump. In either event, hoth pumps are driven at constant speeds and the problem of varying the volume output of such pumps has always existed. It is believed that the present invention overcomes this problem in a practicable manner and in a manner which is mechanically simple and hydraulically efficient.

The invention has been described with particular reference to a preferred embodiment of the invention. It will be appreciated that modifications and alterations will 6 occur'to others upon a reading and understanding of specification and it is my intention to include all such modifications and alterations insofar as they come within the scope of the appended claims.

Having thus described my invention, I claim:

1. A variable volume hydraulic pump comprised of a plurality of members movable relatively to each other and defining a plurality of pumping chambers revolving in a fixed closed path of movement, said chambers gradually increasing in volume after they pass a fixed point of minimum volume on said path of movement until they reach a fixed point of maximum volume on-said path of movement and then gradually decreasing in volume until they reach said fixed point of minimum volume, means defining an arcuate inlet and an arcuate outlet manifold including a pair of lands one at each arcuate end of said manifold and sealingly separating said manifolds one from the other, an opening for each chamber revolving therewith, each of said openings moving past said lands to alternately communicate its associated chamber with either said inlet or said outlet manifold, one of said lands being permanently fixed relative to said path of movement and located at the point of maximum volume so that as each chamber reaches and passes through maximum volume, its opening shifts from communication with the inlet manifold to the outlet manifold, said other land being adjustable along the path of movement of said chambers so as to change the point in the path of movement in which each opening moves past said other land and shifts communication of its chamber from the outlet to the inlet manifold whereby the output volume of said pump may be varied.

2. The combination of claim 1 wherein said lands have a path of movement length at least equal to the path of movement length of said openings and said adjustable land is movable over the arc of increasing volume chambers.

3. In a variable volume hydraulic pump comprised of a plurality of members movable relatively to each other and defining a plurality of pumping chambers revolving in a fixed closed path of movement, said chambers gradually increasing in volume after they pass a fixed point of minimum volume on said path of movement until they reach a fixed point of maximum volume on said path of movement and then gradually decreasing in volume until they reach said fixed point of minimum volume, means defining an arcuate inlet and an arcuate outlet manifold including a pair of lands one at each arcuate end of said manifold and sealingly separating said manifold one from the other, an opening for each chamber revolving therewith, each of said openings moving past said lands to alternately communicate its associated chamber with either said inlet or said outlet manifold, the improvement which comprises one of said lands being permanently fixed relative to said path of movement and located at the point of maximum volume so that as each chamber reaches and passes through maximum volume, its opening shifts from communication with the inlet manifold to the outlet manifold, said other land being adjustable in the path of movement of said chambers so as to change the point in the path of movement in which each opening moves past said other land and shifts communication of its chamber from the outlet to the inlet manifold whereby the output volume of said pump may be varied.

4. The improvement of claim 3 wherein said lands have a path of movement length slightly greater than the path of movement length of said openings and said adjustable land is movable over the arc of increasing volume chambers.

5. The combination of claim 1 wherein said pump includes means sensitive to the pressure output of said pump for adjusting said movable land to maintain the output pressure constant.

6. The combination of claim 5 wherein said lands have a path of movement length slightly greater than the path of movement length of said openings and said movable land is movable over the arc ofinereasing volume chamhers. V

7., The combination of claim 3 wherein said pump includes means sensitive to the output pressure 01; said pump operatively associated with said movable land to adjust same and maintain the output pressure eonstant.

8. T e improvement of claim 7 wherein said lands have a path of movement length slightly greater than the path o mo eme t lengt i p nin n s id mo ab land is movable over the arc of increasing volume chambers.

9. The combination of claim 1 wherein said plurality of members are comprise Of, all internally toothed and an externally toothed meshed gear rotating on spaced axes with the respective teeth having spaced points in sealing engagement and the path of movement length of said openings is the path of movement distance between said points on the teeth.

0- The. combina ion of sl n; 5 cluding Power mew for moving said adjustable st p and m ans ommun cat n said p er means t the u pu Pre sur o said P m References Cited in the file of patent UNITED STATES PATENTS Re. 23,086 Holl Feb. 22, 1949 1,482,807 Newberg Feb. 5, 1924 1,660,464 Wilsey Feb. 28, 1928 2,426,491 Dillon Aug. 26, 1947 2,658,344 Welch Nov. 10, 1953 2,688,927 Nuebling Sept. 14, 1954 2,694,288 Nubling Nov. 16, 1954 2,708,410 Nubling May 17, 1955 2,728,297 'Cilley Dec. 27, 1955 2,771,844 Lipinski Nov. 27, 1956 

